The updated Audi A1 1.6 TDI now emits just 99g/km of CO2.
Tweaks to the fuel system and engine management have dropped CO2 emissions from 105g/km, while average fuel consumption is boosted from 70.6mpg to 74.3mpg.
As before, engine stop-start and energy recuperation systems help to make it as fuel-efficient as possible.
With CO2 emissions dipping below 100g/km the A1 1.6 TDI is now exempt from the London Congestion Charge. Buyers also don't have to pay Vehicle Excise Duty (VED), saving 20 per year compared with the previous 1.6 TDI, which was duty-free in the first year of ownership only.
Prices for the Audi A1 1.6 TDI are unchanged. They start at 14,480 for the SE and rise to 17,865 for the S line model.